This prospective cohort study of the residents of Leisure World Laguna Hills, a retirement community near Los Angeles, is being conducted to evaluate the effects of health-related and life-style practices on disease etiology and prevention in older adults. With this proposal 10 years of follow-up on the cohort members will be completed to provide sufficient numbers of incident cases of several chronic diseases to meet the specific aims of: (1) Evaluating the risks and benefits of estrogen replacement therapy in terms of incident disease and mortality (including endometrial cancer, breast cancer, osteoporotic fractures, acute myocardial infarction, and stroke, plus lymphoma and leukemia, ovarian cancer, rheumatoid arthritis, cholelithiasis, and phlebitis). (2) Investigating the effects of dietary factors, elective drugs, smoking, coffee and alcohol consumption on risk of cancer (including bladder, breast, and colon cancers). (3) Analyzing the associations of cardiovascular and cerebrovascular diseases and exercise, alcohol intake, and aspirin. (4) Assessing the effects of life-style practices on other chronic diseases (including gastrointestinal hemorrhage and ulcers, renal failure, benign prostatic hypertrophy, benign breast disease, inflammatory bowel disease, senile cataracts, and glaucoma). The cohort members, initially enrolled in 1981, number 13987. All members of the cohort will be followed to death or to March 31, 1992. Baseline data from the original questionnaire and updated information from two follow-up questionnaires have already been obtained. The original questionnaire covered basic demographic information, medical history, personal habits, medical screening, vitamin supplement and dietary intake, and (for women) menstrual and reproductive histories. The two follow-up questionnaires asked current intake of vitamin supplements and hormone replacement therapy, recent hospitalizations, and included short dietary sections. Acquisition of all hospital discharge diagnoses for Leisure World residents from three local hospitals and pathologic cancer diagnoses from five local hospitals and from the Cancer Surveillance Programs of Los Angeles and Orange Counties is ongoing. Decedents are identified by reviewing all death certificates of Orange County residents, by the community business office, from the obituary columns of the local newspaper, from information provided by relatives and friends, and by search of the National Death Index. One additional follow-up questionnaire will be sent to all subjects not known to be deceased during the tenth anniversary year of the study, 1991, to verify vital status. The primary method of analysis will be to fit Poisson regression models to group data consisting of multidimensional classification of disease cases and person-years of observation by discrete categories of age, calendar period, and various aspects of exposure. Extension of these models for use with disease rates and exposure variables that vary continuously with age or time (the proportional hazards model of Cox) will also be used.